In applying circuit wires to a printed board the art has relied upon stitch pins or terminals to receive the wire connections for the circuit. The connections are made by electrical bonding or welding, and the termination of a circuit wire has been by cutting with a separate tool having a fixed position relative to the pin, or by the use of a manually operated side cutter. The printed circuits on such boards are small and set close together so that it is sometimes a problem to clear out the end required to be cut off, and the waste of wire is significant.
At present operators of printed circuit board wiring apparatus generally bond up wires for a group of circuits and then retrace the circuit with an illuminated magnifying glass for the purpose of trimming wire ends that might cause problems. The fact that wire ends need to be trimmed means that a quantity of wire is wasted and the time needed to perform the trimming is costly. It is estimated that more than half the time needed to produce a finished printed circuit board is used up in the wire trimming operation. It is also necessary that the operator of apparatus of the type which can perform the wire stitching operation must each time before beginning a circuit manually bend the wire into a position suitable for bonding it to the initial pin in a given circuit. Uniformity of bend is not easily obtained and that leads to waste of the wire and loss of time due to the need to trim excessively long circuit wire ends.
In one arrangement for stitch bonding circuit boards, as discussed in Helda et al U.S. Pat. No. 3,400,448, issued Sept. 10, 1968, a thermal compression bond is made by feeding the circuit wire through a hollow tube so it protrudes and can be arranged to lie across the end of the tube by shears, or by vibrating the tube to sever the wire. The arrangement shown in Steranko, U.S. Pat. No. 3,673,681 issued July 4, 1972 includes circuit board wiring by electrical pulse heating which sublimates the polyurethane insulation and reflow solders the copper wire to the contact pad. The wire is then cut by a flat wire cutter which is fixed in its position at one side of the soldering tip. A different arrangement for effecting wire feed and welding in connection with circuit board terminal pins in shown by Annett, U.S. Pat. No. 3,822,373 issued July 2, 1974. In this prior art reference the wire is outside of the electrode and moves across the electrode face through spaced guides which confine the wire to a single direction of alignment across the electrode. Severing of the wire after the last pin is contacted is not discussed.